Angelique Kerber

Quarterfinal time at the Australian Open: Federer vs Zverev

It's the start of quarterfinals at the Australian Open on Tuesday, and none of the other three will likely be as compelling as the one between Roger Federer and Mischa Zverev.

Federer has 17 Grand Slam singles titles but is playing in his first official tournament in six months after a left knee injury layoff. The 50th-ranked Zverev had a four-set upset victory over top-ranked Andy Murray in the fourth round, a result the 29-year-old lefthander called the best of his career during his post-match media conference .

The 35-year-old Federer looked flawless in beating Tomas Berdych in the third round and then defeated fifth-seeded Kei Nishikori in the fourth round in five tough...